# Oblong endless rack and pinion (mangle rack)

> How does a mangle rack reverse without reversing the pinion?

- Category: Mechanisms › Gears
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 119 (1868)
- Page: https://xemstudio.com/objects/mangle-rack-oblong-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=mangle-rack-oblong-mechanism · Plain text: https://xemstudio.com/objects/mangle-rack-oblong-mechanism/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- The rack is an endless oblong loop of teeth; the pinion, turning always the same way, meshes with the top straight and drives the rack one way, rolls round the half-gear end and comes back along the bottom straight driving it the other way. Its shaft moves up and down 20 mm in a slot as it changes sides.
- Module 1, 20 T pinion; straights 12.57 mm: the rack bar's stroke is the straight length plus the end travel. Drawn with the pinion mid-way along the top straight, its Ø6 axle in the 6.2 mm slot of the catalog guide plate (slot turned vertical).
- Brown's No. 119 (oblong endless rack on a bar, pinion shaft guided by a slotted bar); the mangle rack of Nos. 197–199 is the same idea in a frame.
- Parts (each has its own page): oblong-endless-rack-m1-20t-ends, spur-gears-module-1, slot-guide-plate-90, dowel-pins-metric.
- Brown's movement No. 119 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

## Sizes

| parameter | value |
|---|---|
| pinion | 20 T, module 1, Ø6 axle |
| rack straights | 12.57 mm |
| shaft travel | 20 mm, in a 6.2 slot |
| rack stroke | ≈ 32.57 mm |

## Where the files are

- Henry T. Brown (1868, public domain): [Five Hundred and Seven Mechanical Movements — scan on archive.org](https://archive.org/details/fivehundredseven00browiala) — web — Publisher's page; dimensions are facts
- 507movements.com: [Brown's movement No. 119: figure, his text and an animation](https://507movements.com/mm_119.html) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/mangle-rack-oblong-mechanism/index.json · license: https://xemstudio.com/files/hardware/mangle-rack-oblong-mechanism/LICENSE.md

- mangle-rack-oblong-mechanism-assembly: [STEP](https://xemstudio.com/files/hardware/mangle-rack-oblong-mechanism/mangle-rack-oblong-mechanism-assembly.step) · [STL](https://xemstudio.com/files/hardware/mangle-rack-oblong-mechanism/mangle-rack-oblong-mechanism-assembly.stl) — Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)

## Questions

**How does a mangle rack reverse without reversing the pinion?**

The rack is an endless oblong loop of teeth; the pinion, turning always the same way, meshes with the top straight and drives the rack one way, rolls round the half-gear end and comes back along the bottom straight driving it the other way. Its shaft moves up and down 20 mm in a slot as it changes sides.

## Fits with

- [Oblong endless rack, module 1: two 4π racks joined by 20-tooth half-gear ends](https://xemstudio.com/objects/oblong-endless-rack-m1-20t-ends/)
- [Spur gears, module 1: 10 to 80 teeth (20° involute)](https://xemstudio.com/objects/spur-gears-module-1/)
- [Slot guide plate 90 × 30 × 5, 6.2 mm slot (74 long)](https://xemstudio.com/objects/slot-guide-plate-90/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)